I think it has to do with how Odin saw them. Odin saw Hela as a tool for conquering. Odin saw Loki as a tool for peace with the Jotun. Taika may have meant to highlight that they were both used by Odin with different results by having them look similar.
Directed by Tim Miller. With Ryan Reynolds, Morena Baccarin, T. Miller, Ed Skrein. A former Special Forces operative turned mercenary is subjected to a rogue experiment that leaves him with accelerated healing powers, adopting the alter ego Deadpool.